1. Field of the Invention
The present invention relates to thin parts made of β or quasi-β titanium alloys, and to the manufacture of these thin parts by forging.
More precisely, the invention relates to non-axially symmetrical manufactured parts having a thickness of less than 10 millimeters (mm) made of β or quasi-β titanium alloys, presenting an original microstructure, and a method of manufacturing these parts which, in a characteristic manner, is based on a forging operation.
2. Description of the Related Art
The context in which the presently claimed invention was devised and developed is that of manufacturing single-piece bladed disks (SBD) with blades attached by linear friction welding. Because of their mechanical properties, and in particular because of their ability to withstand vibratory fatigue, such single-piece bladed disks are generally made of β or quasi-β titanium alloy. At present they are obtained by machining a solid blank.
A significant problem existed to date in obtaining the blades of such disks made of β or quasi-β titanium alloy by forging. Forged structures made of β or quasi-β titanium alloys, i.e. structures having large grains, used to make parts of small dimensions (blades), were expected a priori, to have unacceptable mechanical properties (in particular in terms of ability to withstand impacts, and resistance to vibratory fatigue).
In quite a surprising manner, in the context of the present invention, high performance blades (i.e. thin parts) made of β or quasi-β titanium alloys have been obtained (i.e., blades having good metallurgical and mechanical characteristics) by forging, thereby saving material compared with the conventionally-implemented machining technique. These blades also have lifetimes that are longer than the lifetimes of blades obtained by machining; it is possible to make them with optimized shapes, thus improving their aerodynamic performance, and consequently improving the performance of the engine in which they are to be mounted.
The invention has thus been devised and developed in a non-obvious manner in the context of manufacturing single-piece bladed disks (SBD). Nevertheless, the invention is not limited to this context; it is quite naturally equally suitable for contexts that are to some extent similar, such as that of manufacturing single-piece bladed rings (SBR), that of repairing single-piece bladed disks (SBD) and single-piece bladed rings (SBR), and more generally that of manufacturing thin parts out of β or quasi-β titanium.
Control, in accordance with the invention, over the forging of β or quasi-β titanium alloy blanks of small thickness has made it possible to obtain thin parts made of β or quasi-β titanium alloys that are original in terms of their core microstructure.
Such parts constitute the first subject matter of the present invention.
The controlled forging method which leads to such parts constitutes the second subject matter of the invention.